Although any carbonated beverage may produce a foam layer on top of its poured contents, the foam layer on a poured serving of beer is of particular interest to many consumers. The foam layer, referred to as a head, atop a vessel of beer is produced by bubbles of gas, commonly carbon dioxide, that rise to the surface. The compounds that produce the head comprise proteins, yeast and starches in the form of grain residue in the beer. The interaction between the carbon dioxide the proteins and starches in the liquid determine the physical properties of the foam. Carbon dioxide may be produced during fermentation or if the beer is pasteurized it may be carbonated by injecting pressurized gas after pasteurization. Of particular interest to consumers is the density and longevity of the head. As with many reactions, agitation can increase the rate of reaction. Although it is common to produce a head on top of a glass of beer, similarly, foam may also be produced from carbonated soft drinks, carbonated juices or non-alcoholic malt beverages.
It is commonly considered that a greater-than-desired volume of head on the beverage detracts from the mass of the drink, while some head is considered essential to the beverage. The head gives off an aroma of the beer/beverage, and adds to the experience of enjoying the beverage. The production of the head reduces the amount of carbon dioxide in the remainder of the beverage.
While many methods exist for providing a stable, dense head on beer dispensed from casks or pressurized bulk containers, it has long been understood that there are problems associated with attempting to achieve the same effect on beer dispensed from bottles, cans or common single-serve containers. There is a need for a means and apparatus to produce a fine, dense head on a dispensed beer from a variety of disparate containers.